The Marchioness of Worcester will eat bacon sandwiches - as long as it is from "really, really happy pigs".

And that is just the problem for the aristocrat and star of 80s television series Cats Eyes. Some 80 per cent of bacon eaten in Britain is from pork imported from abroad, meaning that the pigs are often raised in "barbaric" conditions well below the UK standard – and we don't even know about it.

The mother-of-three, who married the Marquess of Worcester Henry Somerset in 1987, feels so strongly about the happiness of these "intelligent animals", she decided to make a film about the issue despite little experience of film making.

Pig Business, to be aired next week, is so shocking that drastic cuts had to be made before even Channel 4 would look at it. The film still shows harrowing images of dead animals in pens with other pigs and pregnant sows unable to turn around.

Speaking at her reassuringly shambolic Chelsea home, the Marchioness is angry enough to even allege that swine flu "mutated into a deadly disease" in factory farms.

"The mothers are kept in cages so small they can't turn round for almost all of their entire lives. The fattening pigs are kept in barren concrete compartments deprived of bedding. Their tails are docked to prevent them biting each other in boredom.

The stench from the decomposing effluent – a toxic brew of chemicals not least ammonia and hydrogen sulphide – is damaging the health of the workers and neighbouring villages," she pauses, exhausted with the awfulness of it all.

"This food is not cheap – in terms of damage to human health and the environment it's extremely expensive."

The 50-year-old former actress, who played Miss Scarlett in the first television adaptation of Cluedo, makes an unlikely eco-warrior. Although rather unkempt since her days modelling in Paris in the late 70s, she is still elegant and impossibly posh.

Only the great grand daughter of the Earl of Dudley could pull off a messy chignon, jeans and ethnic cardigan with quite such an artless effect.

But this is not to mistake Tracy Worcester, as she prefers to be known as, as some flaky green activist. She may be parcelled in with the eco-chic crowd along with personal friends Zac Goldsmith and Trudie Styler, but to her credit she has been campaigning on the issue of ethically-sourced food long before it became fashionable.

She has also worked on behalf of Friends of the Earth, the Soil Association and the International Society for Ecology and Culture.

Her film, which was partly self-financed and involved taking a lot of time away from her children, took four years to make. It investigates the growth of factory farming in Eastern European countries like Poland since accession to the EU.

The Marchioness, who acted under the name Tracy Louise Ward, claims that massive subsidies to help these countries to develop are helping big business to move in and replace small farms with massive intensive units.

In other words the UK tax payer is paying for factory farms to put small farmers out of business. It also means that an increasing amount of the cheap meat ending up on our supermarket shelves is reared in conditions well below UK standards.

She saves much of her ire for an American firm Smithfield foods and brings in another eco activist with impeccable breeding – Robert Kennedy of the Presidential Kennedy clan – for comment on depravities of factory farming.

"Why," asks the Marchioness in an exasperated voice, "does the European Bank for Reconstruction and Development lend $100 million (£60 million) to a vast American company? They're putting small Polish farmers out of business. They're putting our farmers, who have to bare the cost of compassionate production methods, out of business too."

Smithfield Foods insist that all the pork they sell in the UK come from farms that "meet and in many cases exceed EU legislation on animal welfare standards and environmental responsibility".

Using techniques more reminiscent of her role in the detective series Cats Eyes or Dr Who in the 1980s, she is filmed jumping over fences before being bundled away by security to try and get footage inside these enormous factory farms in Poland.

But she is also shown wafting around the family kitchen on the family estate of Badminton in Gloucestershire feeding her teenage children sausages and bacon (presumably made from pigs that spent their lives rooting for acorns in the sunshine) before launching into a tirade about the fact that much of the pork labelled as British is in fact only processed in the UK.

This issue first came to light after the Irish pork scandal and since then the UK Government has promised to work with the EU to ensure labels clearly show where the animals was reared.

"Producers are allowed to put 'British produce' on the label, even if it has only been processed in this country," she says. "In order to keep the price low for customers and profits high for supermarkets, cheap ie factory-farmed pork is increasingly coming into this country from the EU where for the next five years sows can be kept in crates.

"Then this barbaric practice will be outlawed. However this is ample time for UK farmers, who are legally obliged to spend more on sows' housing to be undercut by the EU imports and continue to go bankrupt. When factory farms abroad have no competition, they will up the price. We need to buy from UK farmers today or lose them forever."

The Marchioness says her family will be “glad to have their mother back” now the film is over - although they have been incredibly supportive. Her sister, Rachel Ward, the award-winning actress who was in the television series Thorn Birds, has also praised the film.

The aristocrat is the latest high profile name to get excited about where our food comes from.

As well as the usual suspects Jamie Oliver and Hugh Fearnley-Whittingsall, Greta Scacchi was recently photographed hugging a dead cod and Sir Paul McCartney has urged us all to give up meat on Mondays.

Having dropped out of boarding school as a rebellious child, Worcester feels she has never had a proper education and has felt inspired to so something for the planet ever since. She now plans to make more films about the environment.

So is she bothered about being just another celeb on the bandwagon?

She admits that explaining to colleagues in the green movement why her husband's 52,000 acre Badminton estate is not entirely organic can sometimes be tricky- though it is not for want of trying on her part.

However she insists that viewers of her film will not buy more expensive meat because they are told to by "some rich person" but because the small farmers and images in her film persuade them that factory farming is wrong.

"People do care how the food they eat is produced," she says. "It bothers them that their meat comes from a factory rather than a farm. They care about what the factory does to the environment and ultimately to them and their children. They mind that the animal is tortured before they eat it."